Method and system for minimizing disruption during in-service software upgrade

Abstract

A method and a system for in-service software upgrade in a Hot Standby Redundant Distributed (HSRD) system are provided. A standby route processor in HSRD system is updated with upgraded software. The standby route processor is synchronized with an active route processor present in the HSRD system. The control of routing process is switched over to the standby route processor (with the upgraded software) from the active route processor. During the switchover, a minimal context forwarder on the line card begins execution and continues forwarding packets across a network, while a line card in the HSRD system is being reloaded and configured.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of Invention [0002] Embodiments of the invention relate, in general, to upgrading software in a router. More specifically, embodiments of the invention relate to a method and a system for minimizing disruption in forwarding packets during in-service software upgrade. [0003] 2. Description of the Background Art [0004] Routers are often used for forwarding packets across a network based on the Internet Protocol (collectively referred to as IP networks) or on other telecommunication networks. [0005] Routers forward packets by combining hardware-forwarding capabilities with software. For example, a typical router includes a Route Processor (RP) and a number of line cards. The RP performs the routing analysis and determines the next hop for the packets. Each RP controls a plurality of line cards that function as a line terminator for interfacing telecommunication lines from the source to the rest of the network. Since a single line card provide...

AI Technical Summary

Benefits of technology

[0016] In a network, a Hot Standby Redundant Distributed (HSRD) system is often implemented. The HSRD includes routers that include two route processors, one of which is active and other one is standby, collectively referred as the route processors. The route processors share an IP address and a MAC address. The route processors require software for forwarding the packets, which may be modified or upgraded from time to time. During the software modification of the router, the standby route processor is upgraded first and is designated the active route processor while the formerly active route processor is designated the standby route processor. Thereafter, a line card associated with the route processors is upgraded to maintain compatibility with the upgraded software on the active route processor. In one embodiment, during the upgrading of the line card, the line card continues operating under the control of a Minimal Context Forwarder (MCF), which, more specifically, continues forwarding the packets to prevent disruption in the network due to software upgradation. After the reloading of the line card is over, the line card and the upgraded active route processor are both operating with upgraded software and the standby route processor can be upgraded in the background. In this manner, the upgrade process minimized the time during which the forwarding of packets may be interrupted.

Problems solved by technology

However, when the router is off-line, it is unable to forward packet traffic, if the router uses software forwarding line cards.

This results in the requirement for updating the routing tables throughout the network.

During the updating of the routing tables, the packets are still sent in the network but the process of updating the routing tables causes undesirable network congestion, delays, and packet loss.

However, during the changeover to the standby route processor, the forwarding of the packets with the HSRD system may still get disrupted while the software code that controls the CPU on the line cards is updated to maintain compatibility with the standby route processor.

This delay results in some packets being delayed or lost.

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